1. Which measurement (density or conductivity) is more accurate to determine the

ID: 970642 • Letter: 1

Question

1. Which measurement (density or conductivity) is more accurate to determine the salt concentration of a solution? Explain your choice.

2. If a label on the back of a can of soup says that there are 667mg of sodium per 1/2 cup, what is the salt concentration of the soup in %(w/v)?

3. Describe how you would prepare 250 mL of a standard salt solution with a concentration of 7.0%(w/v). Begin with solid NaCl crystals.

4. For each compound indicate whether the resistance of an aqueous solution of the compound would be high or low: Na2SO4, C6H12O6, KCl, CH4N2O

Thank you for the help!

1) conductivity measurement is more accurate as compared to measurement of density directly.

So we can determine concentration by conductivity measurement.

2) 1 US Cup = 236.588 mL

The label is there are 667mg of sodium per 1/2 cup

So 667 mg in 118.294 mL

w/v% = Weight X 100 / volume = 0.667 grams X 100 / 118.294 = 0.264%

3) We need to prepare 250 mL of a standard salt solution with a concentration of 7.0%(w/v)

So this means

7grams / 100mL of solution

so for 250mL we will take = 7 X 2.5 grams of Nacl = 17.5 grams of salt and will make up the solution upto 250mL

4) ionic solutions have high conductivity, non polar compounds have zero conductivity

Na2SO4 will have high conductivity due to highly ionic character

C6H12O6 It is a non polar organic compound , glucose. Will not have any conductivity

KCl = strong electrolyte, high conductivity

CH4N2O = less

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